Linear actuator

ABSTRACT

Plural magnetic sheets ( 22 ) are laminated in circumference direction to form a cylindrical laminated core. Magnetic sheets ( 22 ) adjacent to each other have coupling point ( 25 ) at an upper section or a lower section and gap ( 26 ) on an opposite side of coupling point ( 25 ). Coupling point ( 25 ) is prepared at upper section ( 23 ), then lower section ( 24 ), and upper section ( 23 ) then lower section ( 24 ) alternately. This structure allows assembling a radial laminated core with ease.

TECHNICAL FIELD

[0001] The present invention relates to laminated cores that can beapplied to electromagnetic apparatuses such as linear actuators, lineardynamos, and electromagnetic valves.

BACKGROUND ART

[0002] A conventional linear actuator shown in FIG. 26 is hereinafterdescribed. This linear actuator comprises the following elements:

[0003] inner yoke 10, namely, a laminated core formed of numbers ofE-shaped magnetic plates 8 punched out from thin steel plate by a dieand the E-shaped sheet being arranged in a cylindrical shape radiatingaround a center axis;

[0004] coil 2 wound on slot 1 of inner yoke 10;

[0005] outer yoke 3 formed of numbers of I-shaped magnetic sheetspunched out from rectangular thin steel plate punched by a die, and theI-shaped sheets being arranged in a cylindrical shape radiating aroundthe center axis;

[0006] permanent magnets 5 and 6 disposed in a gap between inner yoke 10and outer yoke 3; and

[0007] vibrator 7 for supporting permanent magnets 5 and 6.

[0008] Permanent magnets 5 and 6 are magnetized in radial direction, andthe magnetic poles of those magnets are arranged such that the inneryoke side of magnet 5 is N pole and the inner yoke side of magnet 6 is Spole. The magnetic poles so arranged, i.e., opposite poles of eachmagnet, are fixed to vibrator 7.

[0009] In the linear actuator structured above, electric current flowingthrough coil 2 generates magnetic flux that forms magnetic pathsindicated with arrow marks. Changing a direction of the electric currentchanges a direction of the magnetic flux flowing from coil 2, andmagnets 5, 6 repeat attraction and repulsion responsive to the change ofthe magnetic flux. As a result, magnets 5 and 6 reciprocate along theaxial direction.

[0010] The conventional linear actuator, however, has the followingproblems:

[0011] (1) Since the conventional laminated cores described above arelaminated cylindrically, each magnetic sheet should be thicker at theouter side of the core and thinner at the inner side of the core. Amagnetic sheet available in the market; however, is constant inthickness across the sheet, thus each one of the magnetic sheets seemsto be cut for changing the thickness to be assembled into theconventional laminated cores. This method is not fit to volumeproduction, or cannot keep the thickness uniform throughout all themagnetic sheets. Thus it is difficult to form a cylindrical shape withthe conventional magnetic sheets.

[0012] (2) Although it is not shown in the drawings, even if a laminatedcore is produced with magnetic sheets having a uniform thickness acrossthe sheet, the adjacent sheets are contact with each other at innerside. However, they have gaps between at outer side, and bonding such asapplying varnish between the sheets and supporting members is required.As a result, the cost increases substantially. Since this laminated coreis a radial laminated body, the magnetic sheets radiate from a center,so that the gap becomes wider toward the outer rim. Thus the total ironamount of the inner yoke, i.e., space factor, lowers, and it isdifficult for the magnetic flux to travel from the permanent magnets tothe thin steel plate.

[0013] (3) In the case of a conventional C-shaped or E-shaped core, themagnetic flux generated from the coil travels along the vibratingdirection on the inner wall side and radial direction on the oppositeside to the permanent magnet. More efficient usage of the magnetic fluxneeds to employ electrical steel sheet of which magnetic property tendsto feed magnetic flux in one direction. This oriented electrical steelsheet tends to feed the magnetic flux in the rolling direction, in factthe magnetic property lowers along right angles with respect to therolling direction. Therefore, in the case of using the steel platepunched out by a die into C-shaped or E-shaped cores, either one of avibrating direction or a radial direction is to use a magnetic propertyhaving a lower permeability along right angles with respect to therolling direction. The magnetic flux generated from the coil thus cannotbe efficiently used.

DISCLOSURE OF INVENTION

[0014] The present invention provides a cylindrical core that is formedby laminating plural magnetic sheets in circumference direction.Adjacent magnetic sheets share a coupler provided at either an upper ora lower section on the outer rim of the laminated core, and gaps areprovided to another side of the couplers. The couplers are provided toan upper section, then at a lower section, an upper section, then alower section alternately. This structure allows assembling a radiallaminated core with ease.

[0015] The present invention provides a cylindrical core that is formedby laminating plural magnetic sheets in circumference direction, and acoupler extending from an end of the magnetic sheet couplers adjacentmagnetic sheets together. This structure allows assembling a laminatedcore with ease.

[0016] The present invention provides a cylindrical core that is formedby laminating plural magnetic sheets in circumference direction, and thecore can be divided in axial direction, so that a coil can be mountedwith ease.

[0017] The present invention provides a cylindrical core that is formedby laminating plural magnetic sheets in circumference direction, andgaps are formed on adjacent sheets at the outer rim side. The core ismolded with resin compound including magnetic powder, therebystrengthening the laminated core.

[0018] The present invention provides a cylindrical core that is formedby laminating plural magnetic sheets in circumference direction. Thecore is formed of a radial laminated body formed by laminating themagnetic sheets in circumference direction and an axial laminated bodyformed by laminating the magnetic sheets in axial direction. Thisstructure allows assembling the laminated core with ease.

[0019] The present invention provides a cylindrical core that is formedby laminating plural magnetic sheets in radial direction, and both theends of the cylindrical shape are bent outward. This structure allowsassembling the laminated core with ease.

BRIEF DESCRIPTION OF DRAWINGS

[0020]FIG. 1 is a sectional view of a linear actuator in accordance witha first exemplary embodiment.

[0021]FIG. 2 shows the interior of an inner yoke in accordance with thefirst exemplary embodiment.

[0022]FIG. 3(a) shows a laminated block viewed from outer rim inaccordance with the first embodiment.

[0023]FIG. 3(b) shows the laminated block viewed from interior inaccordance with the first embodiment.

[0024]FIG. 4 is a sectional view of a compressor.

[0025]FIG. 5 is a partial sectional view of a linear actuator inaccordance with a second exemplary embodiment.

[0026]FIG. 6 illustrates a magnetic sheet in accordance with the secondexemplary embodiment.

[0027]FIG. 7 illustrates a laminated core in accordance with the secondembodiment.

[0028]FIG. 8 shows an inner yoke molded in accordance with the secondembodiment.

[0029]FIG. 9 shows a magnetic sheet having two couplers.

[0030]FIG. 10 is a partial sectional view of an inner yoke.

[0031]FIG. 11 shows an inner yoke in accordance with a third exemplaryembodiment.

[0032]FIG. 12 shows a magnetic sheet in accordance with the thirdembodiment.

[0033]FIG. 13 shows a bent magnetic-sheet.

[0034]FIG. 14 illustrates that an inner yoke is divided.

[0035]FIG. 15 shows an inner yoke.

[0036]FIG. 16 shows a magnetic sheet split into two parts.

[0037]FIG. 17 shows an inner yoke split into two parts.

[0038]FIG. 18 is a partial sectional view of an inner yoke in accordancewith a fourth exemplary embodiment.

[0039]FIG. 19 is a partial sectional view of an inner yoke in accordancewith a fifth exemplary embodiment.

[0040]FIG. 20 is a partial sectional view of an inner yoke in accordancewith a sixth exemplary embodiment.

[0041]FIG. 21 is a partial sectional view of an inner yoke in accordancewith a seventh exemplary embodiment.

[0042]FIG. 22 is a partial sectional view of an inner yoke in accordancewith a eighth exemplary embodiment.

[0043]FIG. 23 is a partial sectional view of an inner yoke in accordancewith a ninth exemplary embodiment.

[0044]FIG. 24 is a partial sectional view of an inner yoke in accordancewith a tenth exemplary embodiment.

[0045]FIG. 25 is a partial sectional view of an inner yoke in accordancewith a eleventh exemplary embodiment.

[0046]FIG. 26(a) is a sectional view of a conventional linear actuator,and FIG. 26(b) is a partial sectional view of an inner yoke of theconventional linear actuator.

BEST MODE FOR CARRYING OUT THE INVENTION

[0047] Exemplary embodiments of the present invention are demonstratedhereinafter with reference to the accompanying drawings.

[0048] Exemplary Embodiment 1

[0049]FIG. 1 shows a structure of linear actuator 11 which comprises thefollowing elements:

[0050] cylindrical inner yoke 13;

[0051] coil 12 wound on inner yoke 13;

[0052] outer yoke 14 disposed outside inner yoke 13;

[0053] permanent magnets 15 a, 15 b which vibrate following the magneticflux generated by coil 12, magnets 15 a, 15 b being disposed in a spacebetween inner yoke 13 and outer yoke 14; and

[0054] cylindrical vibrator 16 for supporting permanent magnets 15 a, 15b. Magnets 15 a, 15 b are fixed on vibrator 16 at its side face facinginner yoke 13. Vibrator 16 has output section 17 at an end foroutputting the vibration. Output section 17 is shaped like a lid ofcylindrical vibrator 16. A resonant spring is mounted to an outputtingshaft of output section 17, and a use of resonance of the spring savespower necessary for vibration, so that driving current running throughcoil 12 can be reduced.

[0055] An integration of the linear actuator discussed above into acompressor shown in FIG. 4 allows highly efficient driving. Linearcompressor 150 comprises the following elements: linear actuator 160,exhausting mechanism 170, spring 171, closed container 172, andsupporter 173. This compressor is fit to an air-conditioner.

[0056] This linear actuator is detailed hereinafter. Inner yoke 13 isformed by laminating rectangular electrical steel sheet, each one of theplates having two recesses, in circumference direction, thereby forminga cylindrical shape. A ring-shaped groove is provided outside of inneryoke 13, and a winding is wound on this ring-shaped groove, so that coil12 is formed.

[0057] Outer yoke 14 is formed by laminating rectangular electricalsteel sheets in circumference direction, thereby forming a cylindricalshape. Inner yoke 13 is disposed inside outer yoke 14. The outer wall ofinner yoke 13 runs parallel to outer yoke 14, and they form a uniformspace in between.

[0058] Ring-shaped permanent magnets 15 a, 15 b are fixed to an innerwall of vibrator 16 by bonding or press-fitting. The magnetic fluxes ofmagnets 15 a, 15 b travel along a radial direction of inner yoke 13, andadjacent magnets 15 a, 15 b have different poles from each other. Themagnetic flux of magnet 15 a travels from inner yoke 13 to outer yoke14, and that of magnet 15 b travels from outer yoke 14 to inner yoke 13.

[0059] The linear actuator structured above allows vibrator 16 tovibrate by changing the current running through coil 12. The currentrunning through coil 12 allows outer yoke 14 and inner yoke 13 to form amagnetic loop, which causes magnetic flux to appear in the space. Magnet15 approaches the magnetic flux. Switching a direction of the currentinverses the magnetic flux traveling in the space, and magnet 15 movesresponsive to the magnetic flux. The switch of the current directionthus vibrates vibrator 16.

[0060] The first embodiment features that adjacent magnetic sheets, madeof electrical steel sheet, are welded in zigzag pattern, therebycoupling the adjacent magnetic sheets like a V-letter to form inner yoke13. FIG. 2 shows a laminated core of which adjacent magnetic sheets formlike a V-letter. This laminated core does not show a cylindrical shapein the drawing because of being simplified for easier description, andactually the magnetic sheets are laminated cylindrically. The core shownin FIG. 2 is detailed hereinafter.

[0061] Inner yoke 13 is formed by laminating rectangular magnetic sheets22 in circumference direction. Each one of the sheets has a uniformthickness across the sheet. Magnetic sheets 22 adjacent to each otherare welded at either one of upper section 23 or lower section 24 on theouter side, thereby forming coupling point 25, and another side ofcoupling point 25 is naturally gapped. Gaps 26 are prepared at an uppersection, then at a lower section, and an upper section, then a lowersection alternately to form zigzag pattern in the circumferencedirection such that the coupling points are provided to a lower section,then an upper section, and a lower section, then an upper sectionalternately. This structure is a feature of inner yoke 13.

[0062] To be more specific, coupling point 25 is provided to only eitherone of an upper section or a lower section of magnetic sheets 22adjacent to each other, and this structure allows the adjacent magneticsheets 22 to be folded in V-letter when sheets 22 are laminated. Whencoupling point 25 of the V-letter is located at upper section 23, thenext V-letter of magnetic sheets 22 has coupling point 25 at lowersection 24. As such, the magnetic sheets folded in V-letter arelaminated in circumference direction.

[0063] On inner side-face 27 of inner yoke 13, coupling point 25 isprepared at an upper, middle and lower sections simultaneously forcoupling adjacent magnetic sheets, so that the adjacent magnetic sheetsare coupled together at inner side-face 27 of inner yoke 13. Around thecoupling points, adjacent sheets are overlaid each other; however, theyare not necessarily overlaid but can be always spaced from each other atconstant intervals using the coupling point.

[0064] A method of manufacturing the foregoing laminated core isdescribed with reference to FIG. 3. First, laminate plural magneticsheets 22 side by side to form a row, then prepare a coupling point bywelding at an end face of outer side of the magnetic sheet which is apart of outer wall of the laminated core. Coupling points 25 are weldedat upper section 23, then lower section 24, and upper section 23 thenlower section 24 alternately like zigzag pattern. If coupling point 25is prepared at upper section 23 on the end face of outer side ofadjacent magnetic sheets 22, no coupling point is prepared at lowersection 24 on the same adjacent sheets, so that the adjacent sheets canbe spaced out at the lower section. Similarly, if coupling point 25 isprepared at lower section 24 on the end face of outer side of adjacentmagnetic sheets, no coupling point is prepared at upper section 23 onthe same adjacent sheets, so that the adjacent sheets can be spaced outat the upper section.

[0065] On inner side of the laminated core, i.e., on inner side face ofmagnetic sheet 22, coupling points 25 are provided to an upper, middleand lower sections for coupling an adjacent sheet to the sheet itself.All the magnetic sheets adjacent to each other are coupled together onlyat the inner side, and the principal faces of magnetic sheets 22 are notintegrated by welding.

[0066] As discussed above, plural magnetic sheets are welded to formlaminated block 30, then the outer side of block 30 is stretched outwith respect to inner side 27 as a center side, so that block 30 isturned into a cylindrical laminated core. Since inner side faces 27 arecoupled together, an inner rim length stay the same even the laminatedblock is stretched out. However, an outer rim length increases due tothe stretching, because adjacent sheets are spaced out where no couplingpoints 25 are available, for they are not completely coupled together.

[0067] In other words, since the outer rim length changes, when theinner side of laminated block 30 is shaped like a cylinder, the outerside is stretched along the laminating direction, so that block 30 turnsinto a cylindrical laminated core. At this time, the outer rim of block30 is extending with the interval between the adjacent sheets beingwidened. However, the adjacent sheets 22 positively have coupling point25 either at upper section 23 or lower section 24, so that the vicinityof coupling point 25 will not open against the stretching along thelaminating direction.

[0068] Coupling point 25 positively couplers parts of each outer sideend-face of adjacent magnetic sheets, so that the stretch of laminatingblock 30 distributes force uniformly to every magnetic sheet. Thisuniform force stretches respective sheets, so that gaps 26 formed by therespective adjacent sheets are opening at even angles, and magneticsheets 22 are laminated in circumference direction at even intervals.

[0069] Without the coupling points on the outer side end-face oflaminated block 30, an effort for making the block cylindrical would befruitless. Because the outer side formed of the magnetic sheets is notstretched by an even force, so that the magnetic sheets cannot belaminated at even intervals in the circumference direction.

[0070] The foregoing method of manufacturing the laminated core refersto the inner yoke of a linear actuator; however, the method is notlimited to the inner yoke, but can be applied to the outer yoke. As longas a laminated core is formed by laminating magnetic sheets incircumference direction, the method can be applied to electromagneticvalves, transformers, and electromagnetic induction heating appliances.The coupling point is not necessarily welded but it can be caulked.

[0071] Exemplary Embodiment 2

[0072] As shown in FIG. 5, the second exemplary embodiment provides alaminated core that includes inner yoke 51 having one coil, vibrator 53being disposed outside inner yoke 41 and having permanent magnet 52, andouter yoke 54 disposed outside of vibrator 53. As shown in FIG. 6, eachone of magnetic sheets 55 has one slot 56, and sheets 55 adjacent toeach other are coupled by coupler 57.

[0073] Magnetic sheets 55 thus coupled are folded at coupler 57 overadjacent sheet 55 so that sheets 55 are laminated radially as shown inFIG. 7. Then the inner wall of the laminated iron core is welded at twosections, i.e., an upper section and a lower section, such that theadjacent magnetic sheets on the circumference are integrated, therebyassembling inner yoke 51.

[0074] At this time, length L1 of coupler 57 shown in FIG. 6 isdesirably equal to interval length L0 between laminated magnetic sheets55. Lead wires 59 and 59′ are provided to inner yoke 51 as electriccoupling means for feeding the coil with power.

[0075] Inner yoke 51 shown in FIG. 7 is a laminated core, and it can bestrengthened by molding, which uses resin compound including iron powderof 65 volume %, to be more specific, thermoset polyester resin is used.(FIG. 8 shows a molded inner yoke.) Another molding method is to fillgaps of inner yoke 51 and spaces of slots, where coils are wound, withresin compound, so that it seems as if a complete stator is integratedinto one independent body. The iron powder included in the resincompound preferably undergoes oxide film treatment so that the powdersurface is covered with oxide film.

[0076] The resin compound having iron powder improves magnetic property,which results in improving motor's efficiency by 2%. This improvement isproportionate to the volume % of the iron powder in the resin compound.In other words, the motor efficiency improves greater as the content ofiron powder increases; however, moldability of the resin compoundlowers, so that the content of iron powder is practically max. 80 volume%. The content not more than 50 volume % does not improve the magneticproperty. Thus an appropriate iron-powder content ranges from 50 to 80%.

[0077] As shown in FIG. 9, coupler 57 can be prepared at two places onmagnetic sheets adjacent to each other.

[0078] In the case of a stator having two coils, two slots 46 can beprovided to magnetic sheet 45 as shown in FIG. 10. This magnetic sheetis laminated to form what is shown in FIG. 11, and two slots 46 areprovided at an upper and a lower sections.

[0079] The magnetic sheet is punched out from electrical steel sheet,and its magnetic property depends on the magnetic property of theelectrical steel sheet. Therefore, an electrical steel sheet withexcellent magnetic property, to be more specific, less iron loss andhigher magnetic flux density, is preferable. Non-oriented electricalsteel sheet is generally used in motors. This steel plate has excellentmagnetic property along every direction of the steel plate.

[0080] Since the magnetic flux of the iron core in the linear actuatorof the present invention travels only along limited directions, i.e.,axial direction and radial direction, so that an electrical steel sheethaving excellent magnetic property in those two directions isacceptable.

[0081] The non-oriented electrical steel sheet has good magneticproperty in any directions, in fact this good magnetic property israther lower than the best direction magnetic property of an orientedelectromagnetic plate to be used for transformers. Therefore, it ispreferable to employ a double oriented electrical steel sheet havingexcellent magnetic property in specified two directions, i.e., rollingdirection and the right-angle direction. Then the magnetic sheets arepunched out from this steel plate such that the axial direction of thesheets agrees with the rolling direction of the steel plate. Themagnetic sheets thus punched out are laminated to form an iron core of astator, whereby the motor efficiency can improve by 2% higher thananother motor that employs non-oriented electrical steel sheet.

[0082] Exemplary Embodiment 3

[0083]FIG. 14 shows an inner yoke that is divided at a slot into twoparts, i.e., an upper and a lower section. Magnetic sheets 74 dividedare formed by the method described in the second embodiment. In thiscase, divided magnetic sheet 69 is punched out in the shape shown inFIG. 12 from electrical steel sheet. Interval L2 between magnetic sheets69 and 69′ is equal to space width L0 on outer wall of the iron corelaminated radially.

[0084] Length L3 of coupler 71 between adjacent magnetic sheets isdetermined by dimensions La, Lb, the foregoing space width L0, and outerdiameter Ld of the stator iron core. To be specific, the followingequation determines L3. L3=L0/Ld×(Ld−La+Lb)

[0085] The magnetic sheet is folded over as shown in FIG. 13 similar towhat is shown in the second embodiment, and laminated radially. Upperinner yoke 72 and lower inner yoke 73 thus divided are preparedrespectively, and coil 74 to be wound on the iron core has been wound insolenoid type in advance and fixed as usual. Then as shown in FIG. 14,coil 74, upper inner yoke 72 and lower inner yoke 73 laminatedindependently are assembled. The assembled body is molded with resincompound, thereby completing an inner yoke.

[0086] In the case of an inner yoke having two coils, a magnetic sheetis divided into three parts, i.e., an upper, middle and lower sections,as shown in FIG. 16. Upper inner yoke 75, middle inner yoke 76 and lowerinner yoke 77 are independently formed. Then those upper inner yoke 75,middle inner yoke 76, lower inner yoke 77 and coils 88, 89 are assembledand molded with resin compound to obtain an inner yoke.

[0087] Exemplary Embodiment 4

[0088] As shown in FIG. 18, inner yoke 83 is formed of three teeth 81and one yoke 82. Each one of teeth 81 is formed by punching outring-shaped magnetic sheets and laminating the sheets axially to form anaxial laminated body. Yoke unit 82 is formed by punching out rectangularmagnetic sheets and arranging the sheets in circumference direction toform a cylindrical shape, namely, yoke unit 82 is a radial laminatedbody. The rectangular magnetic sheet is made from oriented electricalsteel sheet, which has tendency of passing magnetic flux along therolling direction. Due to this tendency the rolling direction of thesteel plate is to agree with a vibrating direction of the vibrator inarranging the magnetic sheets along the circumference direction. Threeteeth 81 are assembled such that inner face of teeth 81 fits to outerface of yoke unit 82, and three teeth 81 are spaced at equal intervalsto reserve a space for coil's winding. Inner yoke 83 thus structuredgenerates magnetic flux by passing electric current through the coilwound on a slot. The magnetic flux flows along the vibrating directionof the vibrator in yoke unit 82, and along radial direction in teeth 81.Therefore, in the case that foregoing inner yoke 83 structured aboveuses E-shaped or C-shaped magnetic sheets punched out from an orientedelectrical steel sheet, either one of the vibrating or radial directioncan use only a better magnetic property instead of a lower permeablemagnetic property directed along right angles with respect to therolling direction that tends to pass the magnetic flux.

[0089] Such a yoke structure is applicable not only to an inner yoke butalso to an outer yoke.

[0090] Exemplary Embodiment 5

[0091] As shown in FIG. 19, inner yoke 87 includes three teeth 83 ofwhich inner wall tilts with respect to the vibrating direction of thevibrator, and outer wall of yoke unit 86 also tilts with respect to thevibrating direction. Teeth 85 are formed by punching out magnetic sheetto form a ring shape along the axial direction and laminating thering-shaped magnetic sheets axially to form an axial laminated body.Yoke unit 86 is formed by punching out rectangular magnetic sheets andlaminating the sheets in circumference direction to form a cylindricalshape, namely, yoke unit 86 is a radial laminated body. The rectangularmagnetic sheet is made from oriented electrical steel sheet, which hastendency of passing magnetic flux along the rolling direction. Due tothis tendency the rolling direction of the steel plate is to agree witha vibrating direction of the vibrator in arranging the magnetic sheetsalong the circumference direction. Three teeth 85 are assembled suchthat inner wall of teeth 85 fits to outer wall of yoke unit 86. Thisfitting requires the tilted faces described above because the faces canbe fitted to each other due to those tilts. The combination of yoke unit86 and teeth 85, both having tilting faces, allows the flow of magneticflux generated from the coil wound on slot 88 to reduce as much aspossible the magnetic flux flowing along right angle directions withrespect to the rolling direction. Because the magnetic flux of orientedelectrical steel sheet is hard to flow along the rolling direction. As aresult, the magnetic flux generated can be more efficiently used.

[0092] Exemplary Embodiment 6

[0093] As shown in FIG. 20, inner yoke 91 is formed of three teeth 99and one yoke unit 90. Three teeth 99 are made from oriented electricalsteel sheet which is punched out into a fan shape. The fan shape isdirected such that the magnetic flux tends to flow along the radialdirection, namely the rolling direction. Teeth block 92 laminated in thevibrating direction of the vibrator are combined into a ring shape toform teeth 99. Yoke unit 90 is formed by punching out rectangularmagnetic sheets and laminating the sheets in circumference direction toform a cylindrical shape, namely, yoke unit 90 is a radial laminatedbody. The rectangular magnetic sheet is made from oriented electricalsteel sheet, which has tendency of passing magnetic flux along therolling direction. Due to this tendency the rolling direction of thesteel plate is to agree with vibrating direction of the vibrator inarranging the magnetic sheets along the circumference direction. Asdiscussed above, the entire inner yoke 91 is formed of orientedelectrical steel sheet, so that the magnetic flux generated from thecoil wound on slot 93 flows along the direction of the better magneticproperty of the oriented electrical steel sheet. As a result, themagnetic flux can be used efficiently.

[0094] Exemplary Embodiment 7

[0095] As shown in FIG. 21, inner yoke 96 comprises the followingelements:

[0096] three teeth 94 of which inner wall tilts with respect tovibrating direction of the vibrator; and

[0097] yoke unit 95 of which outer wall also tilts with respect to thevibrating direction.

[0098] Teeth 94 are made from oriented electrical steel sheet which ispunched out into a fan shape. The fan shape is directed such that themagnetic flux tends to flow along the radial direction, namely therolling direction. Teeth block 97 laminated in the vibrating directionof the vibrator are combined into a ring shape to form teeth 94. Yokeunit 95 is formed by punching out rectangular magnetic sheets andlaminating the sheets in circumference direction to form a cylindricalshape, namely, yoke unit 95 is a radial laminated body. The rectangularmagnetic sheet is made from oriented electrical steel sheet, which hastendency of passing magnetic flux along the rolling direction. Due tothis tendency the rolling direction of the steel plate is to agree withvibrating direction of the vibrator in arranging the magnetic sheetsalong the circumference direction. Three teeth 94 are assembled suchthat inner wall of teeth 94 fits to outer wall of yoke unit 95. Thisfitting requires the tilted faces described above because the faces canbe fitted to each other due to those tilts. The combination of yoke unit95 and teeth 94, both having tilting faces, allows the flow of magneticflux generated from the coil wound on slot 98 to reduce as much aspossible magnetic flux flowing along right angle directions with respectto the rolling direction. Because the magnetic flux of orientedelectrical steel sheet is hard to flow along the rolling direction. As aresult, the magnetic flux generated can be more efficiently used.

[0099] Exemplary Embodiment 8

[0100] As shown in FIG. 22, inner yoke 101 is formed of three teeth 99and one yoke unit 100. Teeth 99 are formed by punching out rectangularmagnetic sheets and arranging the sheets in circumference direction toform a cylindrical shape, namely, teeth 99 are radial laminated bodies.The rectangular magnetic sheet is made from oriented electrical steelsheet, which has tendency of passing magnetic flux along the rollingdirection. Due to this tendency the rolling direction of the steel plateis to agree with vibrating direction of the vibrator in arranging themagnetic sheets along the circumference direction. Yoke unit 100 isformed by punching out rectangular magnetic sheets and arranging thesheets in circumference direction to form a cylindrical shape, namely,yoke unit 100 is a radial laminated body. The rectangular magnetic sheetis made from oriented electrical steel sheet, which has tendency ofpassing magnetic flux along the rolling direction. Due to this tendencythe rolling direction of the steel plate is to agree with the vibratingdirection of the vibrator in arranging the magnetic sheets along thecircumference direction. Three teeth 99 are assembled such that innerwall of teeth 99 fits to outer wall of yoke unit 100, and the threeteeth are spaced at equal intervals to reserve spaces for coils'windings. Inner yoke 101 thus structured generates magnetic flux bypassing electric current through the coil wound on slot 102. Themagnetic flux flows along the vibrating direction of the vibrator in theyoke unit, and along radial direction in the teeth. Therefore, in thecase that foregoing inner yoke 101 structured above uses E-shaped orC-shaped magnetic sheets punched out from an oriented electrical steelsheet, either one of the axial or radial direction can use only a bettermagnetic property instead of a lower permeable magnetic propertydirected along right angles with respect to the rolling direction thattends to pass the magnetic flux.

[0101] Inner yoke 101 is divided into yoke unit 100 and teeth 99,thereby obtaining a greater space factor of the vibrator than the casewhere the yoke is formed by integrating E-shaped or C-shaped vibrator.Further as shown in FIG. 23, yoke unit 105 is divided into inside yokesection 104 and outside yoke section 103 along the vibrating directionof the vibrator, or teeth 108 are divided into inside teeth section 107and outside teeth section 106 along the vibrating direction, therebyfurther increasing the space factor of the vibrator.

[0102] Exemplary Embodiment 9

[0103] As shown in FIG. 24, yoke unit 110 of inner yoke 111 includesthree teeth 109 of which inner wall tilts with respect to vibratingdirection of the vibrator, and outer wall of yoke unit 120 also tiltswith respect to the vibrating direction. Magnetic sheets forming teeth109 are punched out such that the outer wall of teeth 109 is parallel tothe vibrating direction and the inner wall tilts with respect to thevibrating direction because the inner wall fits to yoke unit 110. Themagnetic sheets thus punched out are arranged in circumferencedirection, namely, teeth 109 are radial laminated bodies. Magneticsheets forming yoke unit 110 are punched out such that the inner wall ofyoke unit 110 is parallel to the vibrating direction and the outer walltilts with respect to the vibrating direction because the outer wallfits to teeth 109. The magnetic sheets thus punched out are arranged incircumference direction, namely, yoke unit 110 is radial laminated body.The magnetic sheets discussed above are made from oriented electricalsteel sheet, which has tendency of passing magnetic flux along therolling direction. Due to this tendency, the rolling direction of thesteel plate used in yoke unit 110 is to agree with the vibratingdirection, and the rolling direction of the steel plate used in teeth109 is directed to the radial direction. The combination of yoke unit110 and teeth 109, both having tilting faces, allows the flow ofmagnetic flux generated from the coil wound on slot 122 to reduce asmuch as possible the magnetic flux flowing across the direction alongwhich the magnetic flux of oriented electrical steel sheet is hard toflow. As a result, the magnetic field generated can be more efficientlyused.

[0104] Exemplary Embodiment 10

[0105] As shown in FIG. 25, inner yoke 113 is formed of core blocks 114.Each one of the blocks is formed by stacking rectangular magnetic sheetspunched out to form a laminated body. Both the ends of the laminatedbody are bent by 90 degrees with respect to the laminating direction toform teeth. Core blocks 114 are arranged in circumference direction toform a cylindrical shape, so that inner yoke 113 is completed. Therectangular magnetic sheet is made from oriented electrical steel sheet,which has tendency of passing magnetic flux along the rolling direction.Due to this tendency the rolling direction of the steel plate is toagree with vibrating direction of the vibrator in forming the laminatedbody. In this inner yoke 113 thus structured, magnetic flux generated byfeeding the coil wound on slot 115 with electric current flows along thethickness direction of the oriented electrical steel sheet. Thus themagnetic-flux easy-to-flow direction of the oriented electrical steelsheet agrees with the laminated direction. As a result, the magneticflux can flow efficiently.

INDUSTRIAL APPLICABILITY

[0106] A laminated core to be used in a linear actuator is provided. Thepresent invention allows assembling the laminated core with ease.

1. A laminated core formed by laminating a plurality of magnetic sheetsin circumference direction to form a cylindrical shape; the laminatedcore including: a coupler provided to the magnetic sheets adjacent toeach other at one of an upper section and a lower section on an outerside of the laminated core; a gap provided to another side of thecoupler; wherein the coupler is provided to an upper section, then alower section, and an upper section, then a lower section alternately.2. The laminated core of claim 1, wherein the coupler is disposed on aside face of the outer side of the laminated core.
 3. The laminated coreof claim 1, wherein the coupler is disposed at an end face of the outerside of the laminated core.
 4. The laminated core of claim 1, whereinthe coupler is a welded place which couples the magnetic sheets adjacentto each other.
 5. The laminated core of claim 1, wherein the coupler isa caulked place which couples the magnetic sheets adjacent to eachother.
 6. The laminated core of claim 1, wherein another coupler isprovided on an inner side of the magnetic sheets adjacent to each other.7. The laminated core of claim 1, wherein the magnetic sheets are flatand each one of the sheets has a uniform thickness across each one ofthe sheets.
 8. A laminated core formed by laminating a plurality ofmagnetic sheets in circumference direction to form a cylindrical shape;the laminated core including a coupler, extending from an end of eachone of the magnetic sheets, for coupling adjacent magnetic sheetstogether.
 9. The laminated core of claim 8, wherein the magnetic sheetsand the couplers are unitarily formed and unitarily punched out from anidentical steel plate.
 10. The laminated core of claim 9, wherein eachone of the magnetic sheets is punched out from the steel plate such thatlongitudinal direction of each one of the magnetic sheets agrees withrolling direction of the steel plate.
 11. The laminated core of claim 9,wherein the magnetic sheets are made from double oriented electricalsteel sheet.
 12. The laminated core of claim 11, wherein longitudinaldirection of each one of the magnetic sheets agrees with rollingdirection of the double oriented electrical steel sheet.
 13. Thelaminated core of claim 8, wherein an interval between the adjacentmagnetic sheets in circumference direction is equal to a length of thecoupler.
 14. The laminated core of claim 8, wherein the adjacentmagnetic sheets include the coupler provided at one of an upper sectionand a lower section on an outer side of the laminated core, and a gapprovided to another side of the coupler, wherein the coupler is providedto an upper section, then a lower section, and an upper section, then alower section alternately.
 15. A laminated core formed by laminating aplurality of magnetic sheets in circumference direction to form acylindrical shape; wherein the laminated core is divided axially.
 16. Alaminated core formed by laminating a plurality of magnetic sheets incircumference direction, with a gap formed on outer side of the magneticsheets adjacent to each other, to form a cylindrical shape, wherein thecore is molded with resin compound that includes magnetic powder. 17.The laminated core of claim 16, wherein the resin compound includes themagnetic powder not less than 50 volume %.
 18. The laminated core ofclaim 17, wherein the magnetic powder is iron powder.
 19. A laminatedcore formed by laminating a plurality of magnetic sheets incircumference direction to form a cylindrical shape, the laminated corecomprising: a radial laminated body formed by laminating the magneticsheets in circumference direction; and an axial laminated body formed bylaminating the magnetic sheets in axial direction.
 20. The laminatedcore of claim 19, wherein the radial laminated body is made fromoriented electrical steel sheet of which easy-to-flow direction formagnetic flux of the steel plate agrees with the axial direction of thelaminated core.
 21. The laminated core of claim 19, wherein the axiallaminated body is made from oriented electrical steel sheet of whicheasy-to-flow direction for magnetic flux of the steel plate agrees withradial direction of the core.
 22. The laminated core of claim 19,wherein the axial laminated body is divided into a plurality of piecesin the circumference direction.
 23. A laminated core formed bylaminating a plurality of magnetic sheets to form a cylindrical shape,wherein both ends of the cylindrical shape are bent outside of thecylindrical shape.
 24. The laminated core of claim 23, wherein the coreis divided into a plurality of pieces in circumference direction. 25.The laminated core of claim 23, wherein the core is made from orientedelectromagnetic steel sheet, so that magnetic flux tends to flow from afirst end to a second end of the core.
 26. A linear actuator comprising:a cylindrical outer yoke; an inner yoke disposed inside the outer yokevia a space; a vibrator having a permanent magnet and vibrating in thespace; and a coil disposed in a slot provided to one of the outer yokeand the inner yoke, wherein one of the outer yoke and the inner yokewhichever having the coil is a laminated core formed by laminating aplurality of magnetic sheets to form a cylindrical shape and is definedin any one of claim 1 through claim
 25. 27. A compressor using a linearactuator as a power source, the actuator comprising: a cylindrical outeryoke; an inner yoke disposed inside the outer yoke via a space; avibrator having a permanent magnet and vibrating in the space; and acoil disposed in a slot provided to one of the outer yoke and the inneryoke, wherein one of the outer yoke and the inner yoke whichever havingthe coil is a laminated core as defined in any one of claim 1 throughclaim
 25. 28. A method of manufacturing a laminated core, the methodcomprising the steps of: (a) laminating a plurality of magnetic sheetsto form a laminated body; (b) coupling the laminated body in every othersheet at an upper section of the laminated body with magnetic sheetcoupling means; (c) coupling the laminated body in every other sheet ata lower section of the laminated body with magnetic sheet couplingmeans; (d) the coupling in step (b) and (c) are carried out by weldingin zigzag pattern; and (e) stretching the laminated body welded into acylindrical core.
 29. The method of manufacturing a laminated core ofclaim 28, wherein the magnetic sheet coupling means is laser welding.